Simple Manager

This document explains how to create SNMP management application using NuDesign Multiprotocol C++ Framework.

Here is the listing of the simple manager.

int main(int argc, char* argv[])

{

Initiate use of Ws2_32.dll (windows socket) by a process.

BSocketManager sockMgr;

Create non-volatile storage handler and load parameters. In this case we use file (ascii flat file) as non-volatile storage, handler is implemented in BFileNV class that is a part of NuDesign Multiprotocol C++ Framework.

BFileNV nv;

tInt32 err = nv.ReadFile("SimpleMgr.xnv");

if (err != NDERR_NO_ERROR)

{

cout << "Failed. Err# " << hex << err << endl;

exit(-1);

}

Create UDP transport handler and initialize it. Note that manager requires two transport-endpoints, one for receiving notifications (tarps/informs) and one for sending requests and notifications.

tUint8 tepType[2];

port[0] = 0; // first available

tepType[0] = TETYPE_SEND;

port[1] = 162;

tepType[1] = TETYPE_NOTIFRECV;

BUdpTransport transport;

err = transport.Initialize(port, tepType, 2);

if (err != NDERR_NO_ERROR)

{

cout << "transport init failed" << endl;

exit(-1);

}

SNMP manager requires two callback objects: one to call while handling outgoing requests (error, timeout, report, response) and one to call while handling incoming notifications (trap, inform). The 1^st one must be object of the class that implements ICallbackSnmpOriginator interface, while the 2^nd one has to implement ICallbackSnmpNotifRcvr interface).

CmdGenCB cmdGenCallback(g_ctx);

NotifRcvrCB notifRcvrCallback;

Create SNMP manager. The last parameter is ptr to implementation of ISnmpCrypto interface. This is required only for SNMPv3 operation. If SNMPmanager is to be used for SNMPv1 and/or SNMPv2c then this parameter may be omitted.

BSslCrypto crypto;

BSnmpManager snmpMgr( eSNMPv3,

transport,

&cmdGenCallback,

&notifRcvrCallback,

&nv,

&crypto);

cmdGenCallback.m_pSnmpMgr = &snmpMgr;

Start SNMP manager. SNMP manager creates required modules (engine, message processor, security subsystem, command generator, notification receiver, notification originator), initializes from non-volatile storage, creates receiver and worker(s) threads and returns.

err = snmpMgr.Start();

if (err != NDERR_NO_ERROR)

{

cout << "Failed. err=" << hex << err << endl;

exit(-1);

}

SNMP manager is operating on its own threads so here we want to stop program. Otherwise it’ll exit and destroy the manager (before doing anything useful). This is an example of simple menu system that accepts single character as input and determines what to execute.

char ch = 'a';

while (true)

{

if (ch == 'q')

{

break;

}

// . . .

}

Stop SNMP manager. This will shutdown all the threads, and save the manager’s configuration to non-volatile storage.

snmpMgr.Stop();

{

return 0;

}

Get

To send get request we have to prepare target object and varbind list.

Following code shows how to create varbind list with single varbind for get (or getnext)

request. Note that we need to pass only object identifier of the MIB object to be retrieved. Value part of varbind is automatically set to NULL.

BVarBindList vbl;

BObjectIdentifier oi("1.3.6.1.2.1.1.1.0"); // sysDescr

vbl.Append(oi);

Target object is instance of BSnmpV3Target class. Here is the example how to initialize it.

BSnmpV3Target target;

BAddrINet addr("127.0.0.1:161");

target.address.Set(addr);

target.timeout = 3;

target.numRetries = 1;

Depending of the version of request, security part of the target must be initialized. For SNMPv1 or SNMPv2c, community is required

target.community = "public";

while for the SNMPv3 security model, and security name must be initialized:

target.securityModel = SNMP_SECURITY_MODEL_USM; // 3

target.userName = "md5";

Finally, to send request, call appropriate version of Get method if command generator. Assuming the snmpMgr is instance of BSnmpManager, for v1/v2c get request call

snmpMgr.cmdGen.Get(eSNMPv2c, target, vbl, rqId);

and for v3 request call

snmpMgr.cmdGen.Get(eSNMPv3, target, vbl, rqId,

g_ctx, eSecurityLevel_authNoPriv);

We’ve seen target and vbl, but what is rqId? This is 32-bit integer and it will be set to request id field from the generated get-pdu (it is passed by reference). This should be saved so response could be correlated with request (in the simple manager this value is ignored!).

In SNMPv3 version of Get, there is one more parameter: context. Context is instance of the BContext class and represents (context engine id, context name) from the SNMPv3 scoped PDU. Usually context engine id is equal to authoritative engine id (engine id of the target agent) and context engine id is zero-length string. The implementation of the Simple manager assumes this fact and initializes context engine id and name in the OnReport method of the CmdGenCB class (CmdGenCB implements ICallbackSnmpOriginator interface) when unknownEngineId report is received.

Advanced SNMP managers should allow changing of the context engine id/name to provide correct values for agents with non-default context name(s) or when SNMPv3 proxy forwarding is being used.

Set

Set request is different from Get just in preparing varbind list. For set we have to provide the (new) value for the MIB object.

BVarBindList vbl;

BObjectIdentifier oi("1.3.6.1.2.1.1.4.0"); // sysContact

BObjectSyntax val;

val.SetOctets (“Mr. SNMP”);

vbl.Append(oi, val);